Ala-Gly-Ala

Ala-Gly-Ala is a prototype of a general tripeptide Xxx-Gly-Zzz. Except glycine and proline, there can be 18 possible amino acids for Xxx and another 18 amino acids for Zzz. Ala-Gly-Ala can be used as a model for up to 324 possible motifs of this kind of tripeptide.